To determine whether the
GNAQR183Q mutation is present in the forme frustecases of Sturge-Weber syndrome (SWS) to establish a definitive molecular diagnosis. Methods
We used sensitive droplet digital PCR (ddPCR) to detect and quantify the
GNAQmutation in tissues from epilepsy surgery in 4 patients with leptomeningeal angiomatosis; none had ocular or cutaneous manifestations. Results
Low levels of the
GNAQmutation were detected in the brain tissue of all 4 cases—ranging from 0.42% to 7.1% frequency—but not in blood-derived DNA. Molecular evaluation confirmed the diagnosis in 1 case in which the radiologic and pathologic data were equivocal. Conclusions
We detected the mutation at low levels, consistent with mosaicism in the brain or skin (1.0%–18.1%) of classic cases. Our data confirm that the
forme frusteis part of the spectrum of SWS, with the same molecular mechanism as the classic disease and that ddPCR is helpful where conventional diagnosis is uncertain.